Patent GB-441614-A (GB)
Title: Improvements in piezo-electric hearing-aid devices
IPC: H04R17/00
Filed: 1934-05-23
Abstract: 441,614. Deaf-aids; loud-speakers; receivers. SONOTONE CORPORATION, 19, West 44th Street, New York, U.S.A. May 23, 1934, No. 15457. Convention date, May 24,1933. [Class 40 (iv)] [See also Group XL] A portable hearing-inducing bone vibrator comprises an inconspicuously small vibratory structure of substantial mass actuated by piezoelectric action to translate electric oscillations of audio-frequency into mechanical vibrations and supporting means for said vibratory structure adapted to be held against the soundconducting bone structure of a user whereby the vibratory structure is maintained in floating condition and the hearing inducing vibrations are imparted to the sound-conducting bone structure by reason of the reaction between said vibratory structure and its said supporting means. Such an arrangement is stated to improve low frequency response. Fig. 3 shows a construction of bone conduction hearing aid device comprising a piezo-electric crystal unit 20 consisting of two superposed Rochelle salt strips 21, 22 carrying outer electrode sheets 23, 24 and an intermediate electrode sheet 25. The lower end of the unit 20 is clamped by a bar 30 against a layer of yieldable material 32 on two metal blocks, one of which is shown at 27, the blocks being insulated from each other and secured to the lower end of casing 51. Plug pins 37 carrying the leading-in cord 39 are received in holes 38 in the blocks, one of which is connected by contact strips to the outer electrodes 23, 24 whilst the other is connected by a contact strip to the intermediate electrode 25. A weight 41 is fitted over and attached to the free oscillating end of the unit 20 whilst the casing wall 52 is formed with an elevated portion 53 constituting the contact surface engaging the bone structure of the head of the user. The casing is closed by a two layer cover member 62, 63 having a channel 64 therebetween for receiving one end 65 of a member 66 connected to a head band 67. According to a modification, Figs. 1 and 2 (not shown), the complete casing 51 is omitted, a member in the form of a tongue and corresponding to the wall 52, 53 being provided on one side of the unit whilst the member 66 is attached to the clamping bar 30 on the other side of the unit. According to a modification, Fig. 8, a crystal unit 103 similar in construction to the unit 20, Fig. 3, carries weights 104 at each end and has a clamp 105 secured around its middle portion and connected to the lower bridge wall 106 of a chamber 102 on a spectacle frame 100. If desired, the two-layer crystal units described may be replaced by four, six or multiple layer units. Specification 440,330 is referred to. The Specification as open to inspection under Sect. 91 comprises also constructions in which the clamp surrounding the middle portion of the unit shown in Fig. 8 is connected either to the diaphragm of a telephone receiver or to the apex of a loudspeaker cone. Figs. 13 and 14 (Cancelled), show a construction of loudspeaker employing a pair of crystal units 130, each unit comprising two rectangular crystal plates 131, 132 cut from a Rochelle salt crystal perpendicular to the electric axis and provided with interior and exterior electrode sheets 134 and 133 respectively. Two adjacent edges 135, 136 of each unit are clamped to a cross-shaped rigid supporting member 138 by means of clamping plates 139 with interposed fibre layers 140. The centre part 141 of member 138 is connected to the cone 142 and the unclamped corner of each unit has a weight 143 attached thereto. This subject-matter does not appear in the Specification as accepted.